26,090 research outputs found
Optical Modulation in the X-Ray Binary 4U 1543-624 Revisited
The X-ray binary 4U 1543624 has been provisionally identified as an
ultracompact system with an orbital period of 18~min. We have carried
out time-resolved optical imaging of the binary to verify the ultra-short
orbital period. Using 140\,min of high-cadence -band photometry we recover
the previously-seen sinusoidal modulation and determine a period
\,min. In addition, we also see a 7.0\,mag\,min linear decay, likely related to variations in the
source's accretion activity. Assuming that the sinusoidal modulation arises
from X-ray heating of the inner face of the companion star, we estimate a
distance of 6.0--6.7\,kpc and an inclination angle of
34--61 (90\% confidence) for the binary. Given the
stability of the modulation we can confirm that the modulation is orbital in
origin and 4U 1543624 is an ultracompact X-ray binary.Comment: 6 pages, 3 figures, accepted for publication in Publications of the
Astronomical Society of Australia (PASA
Long-Wavelength Excesses in Two Highly Obscured High-Mass X-Ray Binaries: IGR J16318–4848 and GX 301–2
We present evidence for excess long-wavelength emission from two high-mass X-ray binaries, IGR J16318-4848 and GX 301-2, that show enormous obscuration (N_H ≃ 10^(23)-10^(24) cm^(-2)) in their X-ray spectra. Using archival near- and mid-infrared data, we show that the spectral energy distributions of IGR J16318-4848 and GX 301-2 are substantially higher in the mid-infrared than their expected stellar emission. We successfully fit the excesses with ~1000 K blackbodies, which suggests that they are due to warm circumstellar dust that also gives rise to the X-ray absorption. However, we need further observations to constrain the detailed properties of the excesses. This discovery highlights the importance of mid-infrared observations for understanding highly obscured X-ray binaries
Advanced Meteorological Temperature Sounder (AMTS) simulations
Simulation studies are reported on temperature retrievals from AMTS and their effect on atmospheric analysis. Observations are simulated from radiosonde reports and observed cloud cover. Temperature retrievals are performed and RMS temperature and thickness errors are calculated relative to the radiosonde profiles and compared to similarly generated HIRS statistics. Significant improvement over HIRS is found throughout the atmosphere but especially in the stratosphere and lower troposphere
Blindly detecting orbital modulations of jets from merging supermassive black holes
In the last few years before merger, supermassive black hole binaries will
rapidly inspiral and precess in a magnetic field imposed by a surrounding
circumbinary disk. Multiple simulations suggest this relative motion will
convert some of the local energy to a Poynting-dominated outflow, with a
luminosity 10^{43} erg/s * (B/10^4 G)^2(M/10^8 Msun)^2 (v/0.4 c)^2, some of
which may emerge as synchrotron emission at frequencies near 1 GHz where
current and planned wide-field radio surveys will operate. On top of a secular
increase in power on the gravitational wave inspiral timescale, orbital motion
will produce significant, detectable modulations, both on orbital periods and
(if black hole spins are not aligned with the binary's total angular momenta)
spin-orbit precession timescales. Because the gravitational wave merger time
increases rapidly with separation, we find vast numbers of these transients are
ubiquitously predicted, unless explicitly ruled out (by low efficiency
) or obscured (by accretion geometry f_{geo}). If the fraction of
Poynting flux converted to radio emission times the fraction of lines of sight
accessible is sufficiently large (f_{geo} \epsilon > 2\times 10^{-4}
for a 1 year orbital period), at least one event is accessible to future blind
surveys at a nominal 10^4 {deg}^2 with 0.5 mJy sensitivity. Our procedure
generalizes to other flux-limited surveys designed to investigate EM signatures
associated with many modulations produced by merging SMBH binaries.Comment: Submitted to ApJ. v1 original submission; v2 minor changes in
response to refere
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